1. Field of the Invention
The present invention relates to a piezoelectric/electrostrictive body, a piezoelectric/electrostrictive laminate, and a piezoelectric/electrostrictive film type actuator.
2. Description of the Related Art
Heretofore, a piezoelectric/electrostrictive actuator has been known as an actuator capable of controlling a micro displacement of the order of sub-microns. Especially, in a piezoelectric/electrostrictive film type actuator, a piezoelectric/electrostrictive portion constituted of a piezoelectric/electrostrictive porcelain composition, and a piezoelectric/electrostrictive driving portion having an electrode portion to which a voltage is applied are disposed on a substrate made of a ceramic. This actuator is suitable for the control of the micro displacement, and additionally has superior properties such as a high electromechanical conversion efficiency, a high-speed response, a high durability, and a saved power consumption. These piezoelectric/electrostrictive actuators are used in various applications such as a piezoelectric pressure sensor, a probe moving mechanism of a scanning type tunnel microscope, a rectilinear guide mechanism in an ultra-precision working device, a servo valve for a hydraulic control, a head of a VTR device, a pixel constituting a flat panel type image display device, and a head of an ink jet printer.
Moreover, various investigations are also made with respect to the piezoelectric/electrostrictive porcelain composition constituting the piezoelectric/electrostrictive portion. For example, there is disclosed a Pb(Mg1/3Nb2/3)O3—PbTiO3—PbZrO3 ternary solid solution system composition or a piezoelectric/electrostrictive porcelain composition in which a part of Pb of the composition is replaced with Sr, La or the like (see, e.g., JP-B-44-17103 and JP-B-45-8145). It is expected that a piezoelectric/electrostrictive element having superior piezoelectric/electrostrictive properties (e.g., a piezoelectric d constant) is obtained with respect to a piezoelectric/electrostrictive portion itself that is the most important portion for determining the piezoelectric/electrostrictive properties of the piezoelectric/electrostrictive element.
In recent years, with a rapid industrial development, there is required to be developed a piezoelectric/electrostrictive body or a piezoelectric/electrostrictive film type actuator having more superior piezoelectric/electrostrictive properties that a sufficiently large displacement can be obtained even in a low electric field. However, it cannot be said that a conventional piezoelectric/electrostrictive body or the like sufficiently satisfies such requirement, and there is room for further improvement.
Moreover, in a case where a flexural displacement is repeated a large number of times, there are problems that structural disadvantages such as micro cracks are easily generated in the piezoelectric/electrostrictive portion, a durability rapidly drops, and initial piezoelectric/electrostrictive properties are not exhibited. Furthermore, since a disadvantage such as dielectric breakdown is also easily generated, there is a demand for development of a piezoelectric/electrostrictive body or a piezoelectric/electrostrictive film type actuator which exhibits a sufficient durability even in a case where the flexural displacement is repeated a large number of times.